Interrater reliability of hand-held dynamometry: effects of rater gender, body weight, and grip strength

Clinicians and authors of previous publications have not reached agreement on the interrater reliability of dynametric strength testing. This study investigates the effects of gender, body weight, and grip strength on the reliability of hand-held dynametric strength measurements. Ten male and 10 female raters tested five muscle groups on the same two subjects (one male and one female) with a Chatillon Series D hand-held, spring-scale dynamometer. Both the raters and the test subjects were blinded to the dynametric output readings throughout the testing. Interrater reliability was good for all tests except for female raters when testing the male subjects' stronger muscle groups. Standard deviations were 61% and 50% greater for female vs. male raters for elbow flexors and knee extensors, respectively. Female raters' body weight had a significant correlation with torque when testing male subjects' wrist extensors, ankle dorsiflexors, and knee extensors (r > 0.64). Likewise, female raters' grip strength significantly correlated with torque when testing males' wrist extensors and elbow flexors (r >/= 0.71). The results indicate that gender, body weight, and grip strength affect a rater's ability to stabilize a hand-held dynamometer and could influence reliability when testing stronger muscle groups. J Orthop Sports Phys Ther 1992;16(2):74-81.